Real-Time Circuit Pressures Correlate Poorly with Circuit Longevity in Anticoagulant-Free, Predilution Continuous Venovenous Hemofiltration

Background: Continuous venovenous hemofiltration (CVVH) in renal failure is compromised by circuit clotting. We hypothesized that adverse circuit pressures are predictive of clotting in circuits that last less than 24 h during predilution, anticoagulant-free CVVH. Methods: This was a single-center retrospective study of 63 CVVH circuits of 13 critically ill intensive care unit patients with severe renal failure. Circuits were categorized into ‘clotters’ (C) or ‘nonclotters’ (NC), if spontaneous clotting occurred at <24 or ≧24 h from the start of CVVH, respectively. Results: Effluent pressures and pre-filter pressures were more adverse in NC compared to C starting from 6 and 4 h before spontaneous clotting, respectively. Arterial pressures and return pressures were not significantly different in C versus NC. Blood flow rate settings, hemofiltration fluid replacement and effluent drainage rates in C versus NC were comparable. Conclusion: Real-time circuit pressure readings seem to offer only potentially limited prognostic value in predicting circuit clotting.